Im sure any good machine shop can do it , its getting them to actually do it.
I bought a upper kit from Sarco years ago it came with a virgin barrel
No front sight “holes” and in the white.
I ended up buying a front sight base with set screws. I mounted the sight with the screws and got it all centered and zeroed.
With a steady hand I made flats on the barrel for the set screws to sit on. Also gave me wiggle room for windage adjustment by front sight.
Once I was happy I drilled a 5th set screw up through the bottom to lock it down real good.
You can also ship it to ADCO, WOA and others .
Sorry my luck with gun smiths has been low in this area.
Thanks for the replies. I was hoping to stick with the original tapered pin design, but I'll just drill and tap a couple holes in the fsb and dimple the barrel .
Someone had posted some photos of a car15 and I was bit intrigued by the shorter barrel and extended flash hider, and with some parts lying around , figured I'd try and assemble something.